Positive control of the steering angle of the nose landing gear wheel is mandatory for precise ground maneuvering of any modern aircraft. A small maximum nose wheel turning angle is desirable for high aircraft speeds such as occur during takeoff and landing runs, while a large maximum nose wheel turning angle is necessary for low speed taxiing and parking operations.
Conventional practice with small airplanes is to connect the rudder pedals of the aircraft to the nose wheel through light bungees or springs. Therefore, when contra turning forces are low such as during taxi operations, the nose wheel can be turned through large angles whereas at high speed operations where the contra turning forces are high, the bungees supply relatively small forces to the wheel which result in relatively small turning angles.
For large aircraft, where the nose wheel must be powered by some sort of auxiliary means, such a solution has not been practical and two separate controls are normally used for nose wheel steering, one during taxi operations and the other during high speed operations. In this latter example the rudder pedals are operatively coupled to the nose wheel power steering to provide the small angle inputs required for high speed operation whereas a separate wheel type control is used for the large angle control inputs needed for low speed operation. Two different controls for the same function are not desirable, and the wheel control has traditionally required a rather large amount of cockpit panel or console space. Frequently, this control is accessible only to the pilot since space between the pilot and the co-pilot is normally at a premium. This is undesirable since it means that the aircraft only can be completely controlled and flown from the pilot's position.